Bioavailability of gatifloxacin by gastric tube administration with and without concomitant enteral feeding in critically ill patients.

Objective: Sequential intravenous-to-oral antimicrobial therapy with highly bioavailable antiinfective agents such as the fluoroquinolones may improve patient safety and decrease cost of infection management. However, physiologic changes associated with critical illness may alter drug absorption, distribution, and clearance, and concomitant enteral feeding may decrease fluoroquinolone bioavailability. We evaluated the effect of critical illness and concomitant gastric tube feeding on gatifloxacin bioavailability.

Design: Prospective, randomized, single-dose, two-way crossover, pharmacokinetic study. SETTINGA tertiary, level-one, trauma center.

Patients: Sixteen critically ill patients (baseline Acute Physiology and Chronic Health Evaluation II score >or=16) tolerating enteral nutrition administered by gastric tube (NG) for >or=12 hrs were randomized to receive gatifloxacin concurrently with continuous tube feeding or with interrupted tube feeds. Patients with renal insufficiency or those receiving concomitant fluoroquinolone therapy or postpyloric feeding were excluded. Patients received gatifloxacin 400 mg either by the intravenous or NG route followed by the alternative dosage form after a 72-hr washout period.

Measurements And Main Results: Serial serum gatifloxacin concentrations (from 5 mins to 24 hrs) were analyzed using a validated high-performance liquid chromatography method. Bioavailability was determined as the ratio of NG/intravenous area under the concentration-time curve (AUC infinity ) measured by the trapezoidal method. Although there was no difference in the bioavailability between NG (AUC infinity : 38.0 [range 20.1 to 48.5] microg x h/mL) and intravenous (AUC infinity : 39.5 [range 24.1 to 63.1] microg x h/mL, p =.60) gatifloxacin (bioavailability: 98.5% [range 61.1% to 119.7%]), a wide variability was observed in three of eight patients (>30% reduction in bioavailability). Concomitant gastric tube feeding did not affect gatifloxacin bioavailability (interrupted tube feeds: 98.5% [range 61.1% to 119.7%]; continuous tube feeding: 109.0% [range 86.2% to 142.1%]; p =.42). Neither a period nor differential carryover effect was observed.

Conclusions: Although concomitant tube feeding did not affect gatifloxacin bioavailability, critical illness resulted in significant variability that may complicate the role of gatifloxacin in sequential intravenous-to-oral therapy. More research is needed to identify those patients in whom gatifloxacin bioavailability is reduced and for whom an empirical increase in gatifloxacin dose should be considered.